Rim Fire

Rim Fire

A U.S. Forest Service firefighter monitors the Rim Fire in Groveland, Calif., Aug. 22, 2013.

Credit: Justin Sullivan/Getty Images

Inmate firefighters walk along Highway 120 as firefighters continue to battle the Rim Fire near Yosemite National Park, Calif., on Sunday, Aug. 25, 2013. Fire crews are clearing brush and setting sprinklers to protect two groves of giant sequoias as a massive week-old wildfire rages along the remote northwest edge of Yosemite National Park.

Credit: AP Photo/Jae C. Hong

A firefighter watches for spot fires during a burnout operation while battling the Rim Fire near Yosemite National Park, Calif., on Sunday, Aug. 25, 2013. Fire crews are clearing brush and setting sprinklers to protect two groves of giant sequoias as a massive week-old wildfire rages along the remote northwest edge of Yosemite National Park.

Credit: AP Photo/Jae C. Hong

A wildfire is threatening more than 4,500 homes in California - about half of which are in Pine Mountain Lake - from a fire that ranks among the 20 worst the state has ever seen.